The present invention relates generally to testers for the brake systems of a rail car and more specifically to leakage testing of a brake cylinder.
The American Association of Railroads ("AAR") has recently approved and required the installation and use of a pressure tap for brake cylinder pressure measurement. With this additional requirement, various rules have been promulgated for brake cylinder tests. Rule 88.C.2.c.(1) requires that units be tested to insure that the brakes were applied for a minimum of four hours from a service reduction of brake pipe pressure to zero psi from a 70 psi brake pipe charge. Another proposed test is that the brake cylinder leakage not exceed 4 psi in ten minutes after a 40 psi reduction from a 90 psi brake pipe charge. The leakage test should start 3 minutes after the 40 psi reduction is made. These tests are not only performed in the field, but at the car manufacturers, when the brake equipment is applied to the car.
Various single car testers have been proposed, but none of them have been directed to these new proposed tests. It is also desirable to provide a test which is a simulation of the four hour service brake reduction test that is performed in under an hour.
The present invention is a test device and a method of testing leakage of a brake cylinder on a railroad car having a brake pipe and brake valve. The method includes charging the brake pipe, discharging the brake pipe at least at a service rate to actuate the brakes by charging the brake cylinder and simultaneously with charging the brake cylinder charging a reference volume to the brake cylinder pressure. Discharging of the brake pipe is terminated and the pressure in the reference volume is maintained. The difference of pressure between the brake cylinder and the reference volume, at a fixed period after the beginning of maintaining the pressure in the reference volume, is measured to determine the leakage.
The measuring of the difference to determine the leakage is performed by determining if the difference in pressure is between the reference volume and the brake cylinder after the fixed period is above a preselected value. For a first test, the brake pipe is discharged to zero. The period and the preselected value are selected to simulate a four hour test in under an hour. The fixed period is preferably between four and 30 minutes. For the second test, the brake pipe is discharged or reduced by 40 psi. The pressure in the reference volume is maintained three minutes after termination of discharging. The fixed period is ten minutes.
The car generally includes a car reservoir for charging the brake cylinder and the reference reservoir is also charged from the car reservoir. The determined leakage is compared to a preselected leakage and a determination of pass/fail is made from the comparison. The test is performed using a portable tester which includes the reference volume and ports to be connected to a source of pressure, to the brake pipe and to the brake cylinder.
A leakage tester for a brake cylinder on a railroad car having a brake pipe and a brake valve includes a housing having a source port, a brake port and a brake cylinder port. A first valve connects the source port to the brake pipe port and controls the charging and discharging of the brake pipe. A reference volume is provided and a second valve connects the brake cylinder port and the reference volume and controls the interconnection of the brake cylinder port and the reference volume. A first timer is provided set to a fixed period. A first sensor is connected to the reference volume and the brake cylinder port and determines the pressure difference between the reference volume and the brake cylinder port. A first indicator is connected to the first sensor and the timer and indicates pass/fail at the expiration of the fixed period.
The first valve has a first position connecting the brake pipe port to the source port and a second position connecting the brake pipe port to exhaust. A second valve is connected to the brake pipe port and has a first position connecting the reference volume to the brake cylinder port and a second position disconnecting the reference volume from the brake cylinder port. For the first test, the second valve is in the first position for brake pipe port pressure above a first valve and the second position for brake pipe port pressure below the first valve. For the second test, the second valve is controlled by a second timer to move from the first to the second position at the expiration of the period of the second timer.
A second sensor is connected to the brake pipe port and determines the charging state of the brake pipe. The second sensor may include a flow sensor and a pressure sensor. A second indicator is connected to the second sensor and indicates the charging state of the brake pipe. For the first test, the second sensor is connected to the first timer to initiate the first timer for preselected charge state of the brake pipe. The preselected state is preferably discharged to substantially zero brake pipe pressure. For the second test, the second sensor initiates the second timer and the expiration of the second timer initiates the first timer. The preselected state is a preselected reduction. A third valve connecting the exhaust to the first valve controls the reduction.
A third sensor is connected to the brake cylinder port and determines the charge state of the brake cylinder. Where a third sensor is provided, the second and third sensors are connected to the first timer to initiate the timer for a preselected charge state of the brake pipe and brake cylinder.
A third indicator is connected to the timer and indicates the test start/end. The first indicator is connected to the first sensor and the first timer and indicates pass/fail after expiration of the first timer's period. A latch holds the first indicator in the pass state. The latch is reset after the period in response to recharging the brake pipe port. The timers are also reset after the period in response to recharging the brake pipe port. The fixed period is between four and 30 minutes, and the period, the sensor and the indicator simulate a four hour leakage test in under an hour. For the second test, the second timer's period is at least 3 minutes and the first timer's period is at least 10 minutes.
The tester is portable and weighs less than 50 pounds. The reference volume is in the housing. An on/off switch is provided in series with a battery and connected in circuit with the timer, sensor and indicator.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.